The proceeding Korean patent number of 10-0766520 (title of invention: Speaker Having Video Screen Function) filed by the same applicant as the present invention discloses a technology in which a conventional speaker cone paper is substituted with a flexible OLED or a flexible OLED is covered on a speaker cone paper, and various video images are displayed on a flexible OLED in sync with audio.
FIG. 1 is a view illustrating the construction of a conventional visual speaker which is formed of a voice coil 24, a magnet 26, an edge 23, an external gasket 20 and a flexible OLED 21. The video images provided from a video/audio PCB chip are displayed on a flexible OLED.
Since the above visual speaker is configured using a flexible OLED instead a conventional cone paper or a flexible OLED is covered on a cone paper, it weighs more than a synthetic resin device or a paper material which are typically used as the material of a cone speaker, so it is not easy to control the quality of sound. In order to overcome the above problems, a voice coil might be wound more depending on the increased weight so as to increase the power, but the whole volume of the speaker increases, and power consumption increases, which leads to an inefficient operation.
The conventional visual speaker is equipped with a plurality of cables at both ends of a speaker cone paper for processing video signals. In order to obtain a substantial resolution, more cables are needed thereby interrupting the movement in edges. When a coated cable is used so as to prevent the oxidation of electric cables, thinner cables are needed along with increased weight.
In case of a conventional speaker, additional characteristics such as a diameter of a speaker, a voice coil, and a corrugation are determined depending on an outer characteristic and a response characteristic. As a speaker cone and a voice coil attached to the speaker cone operate, an electric output is converted into vibration energy. The corrugation is very important in a sound quality design of a speaker because the corrugation damps so as to prevent the speaker from moving so that the speaker cone and the voice coil can be fixed in position. As the time needed for the speaker cone paper to vibrate and return back to a center position is extended, the clarity of sound degrades, so it is needed to increase a damping factor which represents an attenuation characteristic of speaker sound. The method for enhancing a damping factor can be adjusted depending on an amplifier design, a cable loss and a speaker enclosure type, but as a method for adjusting a damping factor in its own unit, no other methods exist except for a corrugation method.
In particular, in case of a voice coil, a thickness is decreased so as to make the speaker smaller, while increasing the output. However, in case of a corrugation device, the size of a corrugation is increased in proportion to the size of a speaker cone paper so as to obtain a desired damping effect of a speaker cone paper, therefore it is impossible to make the corrugation smaller. The corrugation is mainly made of a resin cloth, so it feels hard and flexible. However, their natural characteristics might be degraded depending on the time of use, so tones can change.